RIVERS (10IGCSE) Flashcards
(26 cards)
Where are river valleys common in a river- upper or lower course?
Upper course- result from erosion by river and weathering. Large bedload carried due to high discharge, eroding bed and valley by abrasion.
As river channels and valleys deepen, sides of the valley become more susceptible to weathering T or F
T
What type of valley did glacial erosion created? V or U
U
They moved slowly down mountain slopes during last glaciation
How are waterfalls created?
Change in rock type resulting in differential erosion
A waterfall forms when resistant rock is higher than less resistant rock type
T
What happens eventually to the more resistant rock (rock cap) on top of waterfall?
Collapses, as it is unsupported at base due to least resistant rock being undercut/eroded
What is the name of the landform that is left behind when a waterfall retreats
Gorge (deep sided valley)
Do waterfalls constantly retreat upstream or downstream?
Upstream towards source due to undercutting
What are potholes
Cylindrical holes drilled into riverbed
Where are potholes usually found in rivers
Upper course- load is large, mainly transported along bed
What are rapids
Sections of a river where the gradient is relatively steep and composed of mainly hard rocks- increasing turbulence and velocity
Bends in rivers that form as the river’s sinuosity increases
Meanders
The measurement of how much a river varies from a straight line
Sinuosity
A sinuosity of 1 means
River perfectly straight
On meanders, erosion occurs on which side?
Outside bend
On meanders, deposition occurs on which side?
Inside bend
What is the U-shaped body of water formed when a meander gets cut off from main flow after the neck narrows from increased erosion, deposition?
Oxbow lake
Depositional landform found at mouth of river when it meets body of water with lower velocity
Delta
What type of water is required for a delta to form?
Quiet with low tidal range, so deposition can accumulate
How do deltas spread?
The main river channel gets blocked due to river’s load being deposited. Water is forced to find alternative routes to sea.
Do deltas have very fertile soil
Y
What is a levee
natural embankment produced when river floods (deposits load over flood plain due to dramatic drop in river velocity as friction increases)
What is a floodplain
Large, flat expanse of land on either side of rivers- the area the river floods when experiencing high discharge
Are floodplains very fertile
Y- when rivers flood they are forced to deposit load
